Personal mobility devices are vehicles designed to transport one person at a time, usually with room for a small amount of cargo. These devices may be operated while standing, such as with the Segway Personal Transporter, or they may be operated while sitting, such as with a common wheel chair.
Personal mobility devices with wheels may be propelled either manually (by turning the wheels by the hand) or by various automated systems. For example, electric powered wheelchairs (EPWs) use electric motors to move the wheels. They are usually powered by 4 or 5 amp deep-cycle rechargeable batteries, similar to those used to power outboard boat engines.
EPWs are typically operated using a joystick on a controller that controls the speed and direction. The wheels may be turned at variable speed in either direction, giving the chair a zero-turning-radius capability and making navigation through relatively narrow pathways possible.
However, wheels present disadvantages, particularly when the terrain is soft or uneven, as may be the case outdoors. In soft ground, the weight of the vehicle and occupant causes the wheels to sink into the ground and become difficult to turn. On uneven terrain, including curbs and stairs, the wheels may be difficult to roll over a significant change in height.
One alternative to wheeled vehicles is a tracked vehicle that uses a continuous track instead of wheels. The tracks are in contact with a larger surface area than would generally be the case with wheels, and thus exert a lower force per unit area on the ground being traversed than a conventional wheeled vehicle of the same weight. This makes them particularly suitable for use on soft, low friction and uneven ground such as mud, ice and snow.
There are disadvantages to tracked vehicles too, though. For example, prior art tracked devices typically contact the ground with a long and wide footprint, and therefore require and use significant power to overcome the resistance of friction during movement. Also, tracked vehicles can cause significant damage to carpets or floors when used indoors, since the track presents a large contact area with the floor as described above. Further, the turning radius of a tracked vehicle is typically larger than the turning radius of a wheeled vehicle due to the length of the track.
Applicant's U.S. Pat. No. 8,371,403 sought to address problems associated with prior art mobility vehicles by providing, in one embodiment, a tracked mobility device comprising: a) a pair of independent, self-supported track drives having a ground contact area; wherein each of said independent, self-supported track drives comprises: i) a drive wheel; ii) a plurality of rollers; and iii) a flexible track; and iv) a frame; wherein said frame holds said drive wheel, said plurality of rollers, and said flexible track in an aligned orientation wherein the track drive may function as an independent, self-supported assembly; b) a body connected to said pair of independent track drives in a manner that allows each track drive to independently tilt upward or downward with respect to the body as the device moves forward or rearward on its tracks; c) a seat supported by said body; d) a controller to control the speed and direction of rotation of each of the track drives; e) a multi-directional wheel having a first, raised position above the plane of said planar ground contact area, and a second, lowered position below the plane of said planar ground contact area; and f) an actuator effective to lower said multi-directional wheel to its lowered position, wherein the actuator lowers said wheel an amount sufficient to raise at least part of said track drive ground contact areas from the ground when the device is resting on the ground without raising all of said track drive ground contact areas from the ground.
In another embodiment applicant's U.S. Pat. No. 8,371,403 provides a tracked mobility device, comprising: a) a first self-supported, independent track drive comprising: i) a first motor operably connected to a first drive shaft; ii) a first drive wheel connected to the first drive shaft; iii) a first plurality of rollers aligned with said first drive wheel; iv) a first track; and v) a first pair of spaced-apart frame members effective for holding the first plurality of rollers in an aligned orientation; wherein said frame members additionally assist in holding the first track drive together as a self-supported, independent assembly; b) a second self-supported, independent track drive comprising: i) a second motor operably connected to a second drive shaft; ii) a second drive wheel connected to the second drive shaft; iii) a second plurality of rollers aligned with said second drive wheel; iv) a second track; and v) a second pair of spaced-apart frame members effective for holding the second plurality of rollers in an aligned orientation; wherein said frame members additionally assist in holding the second track drive together as a self-supported, independent assembly; c) a body jointly supported by said first self-supported, independent track drive, and by said second self-supported, independent track drive in a manner that allows each track drive to independently tilt upward or downward with respect to the body as the device moves forward or rearward on its tracks; d) a seat supported by said body; and e) a controller to control the speed and direction of rotation of each of the track drives.
In yet a further embodiment applicant's U.S. Pat. No. 8,371,403 provides a tracked mobility device, comprising: a) a pair of track drives, each of said track drives defining a planar ground contact area, wherein said pair of planar ground contact areas are coplanar, wherein each of said ground contact areas including a forward ground contact area and a rearward ground contact area; b) a first castor wheel having a first, raised position above the plane of said ground contact areas, and a second, lowered position below the plane of said ground contact areas; c) a second castor wheel having a first, raised position above the plane of said ground contact areas, and a second, lowered position below the plane of said ground contact areas; d) a first actuator effective to lower said first castor wheel to its lowered position; e) a second actuator effective to lower said second castor wheel to its lowered position; wherein said first actuator and said second actuator cooperate to lower said first castor wheel and said second castor wheel an amount sufficient to raise one of said forward and rearward ground contact areas of each track drive from the floor when the device is resting on the floor without raising the other of said forward and rearward ground contact areas of each track drive from the floor; f) a body connected to each of said pair of track drives in a manner that allows each track drive to independently tilt upward or downward with respect to the body as the device moves forward or rearward on its tracks; g) a seat supported by said body; and h) a controller to control the speed and direction of rotation of each of the track drives.
A need continues to exist, however, for improvements to applicant's personal mobility vehicle to improve the low-friction, quick-turning, indoor and outdoor drivability of the device while still providing the superior off-road capability of a tracked vehicle. The present invention addresses that need.